1. Field of the Invention
The invention relates to novel adeno-associated virus (AAV) vector constructs designed to express recombinant full length immunoglobulins or fragments thereof. The AAV vectors may be used for ex vivo or in vivo expression of a heterologous immunoglobulin coding sequence by a cell or organ, or in vitro for the production of recombinant immunoglobulin by AAV transduced cells.
2. Background of the Technology
Monoclonal antibodies have been proven as effective therapeutics for cancer and other diseases. Current antibody therapy often involves repeat administration and long term treatment regimens, which are associated with a number of disadvantages, such as inconsistent serum levels, limited duration of efficacy per administration such that frequent readminstration is required and high cost. The use of antibodies as diagnostic tools and therapeutic modalities has found increasing use in recent years. The first FDA-approved monoclonal antibody for cancer treatment, Rituxan® (Rituximab) was approved in 1997 for the treatment of patients with non-Hodgkin's lymphoma and soon thereafter in 1998, Herceptin®, a humanized monoclonal antibody for treatment of patients with metastatic breast cancer, was approved. Numerous antibody-based therapies that are in various stages of clinical development are showing promise. One limitation to the widespread clinical application of antibody technology is that typically large amounts of antibody are required for therapeutic efficacy and the costs associated with production are significant. Chinese Hamster Ovarian (CHO) cells, SP20 and NSO2 myeloma cells are the most commonly used mammalian cell lines for commercial scale production of glycosylated human proteins such as antibodies. The yields obtained from mammalian cell line production typically range from 50-250 mg/L for 5-7 day culture in a batch fermentor or 300-1000 mg/L in 7-12 days in fed batch fermentors. High level production often relies upon gene amplification and selection of best performing clones which is time consuming and further increases the cost of development and production. In addition, stability issues with respect to antibody-producing cell lines are often evident following multiple passages.
There remains a need for improved systems for the production of full length immunoglobulins and fragments thereof in vitro and in vivo for therapeutic use.
Adeno associated virus (AAV) is a preferred vector for delivering therapeutic genes due to its safety profile and capability of long term gene expression in vivo. Recombinant AAV vectors (rAAV) have been previously used to express single chain antibodies in vivo. Due to the limited transgene packaging capacity of AAV and its low transduction efficiency, it has been a technical challenge to express heavy and light chains of an antibody using a single AAV vector in order to generate full length antibodies.
The present invention addresses this need by demonstrating the feasibility of a novel approach for achieving high and consistent serum levels of full length antibodies following a single injection of a recombinant AAV vector.